1. Field of the Invention
This invention relates to a real-time endoscopic image processing system for processing endoscopic images on a real-time basis, and more particularly to a system for sampling signals corresponding to the brightest point at the central portion of each fiber element of an image fiber which is used for capturing an image of the internal portion of a capillary vessel by means of a television camera, and effecting the interpolation process by use of the sampled signals to create and output a video signal when the picture image is enlarged and displayed on a video monitor for observation.
2. Description of the Related Art
The diseased part of a human body may be observed by inserting an image fiber catheter for capillary endoscopy into the diseased part of a blood vessel. In the prior art for effecting the above observation, the internal portion of the blood vessel is photographed with a small television camera 1400 mounted on an eye piece 1200 of an image guide 1000 of a fiber catheter for capillary endoscopy as shown in FIG. 1. An enlarged image created based on a video signal output from the television camera 1400 is displayed on a monitor 1600 and the enlarged image is observed to diagnose the diseased part.
More specifically, an image T1 of the internal portion of the vessel obtained on the eyepiece end face lOOOA of the image guide 1000 is enlarged by the eye piece 1200 and an enlarged image T2 of the internal portion of the blood vessel output from the eye piece 1200 is captured by the television camera 1400.
A video signal T3 output from the television camera 1400 is input to the monitor 1600 to display the enlarged image on the image screen thereof.
In the above-described prior art, each of the fiber elements constituting the image guide 1000 has a portion called a core for permitting transmission of light and a portion called a clad for inhibiting transmission of light as is well known in the art.
A net pattern associated with the pixel arrangement on the output plane of the image guide 1000 is formed on the image T1 of the internal portion of the blood vessel created on the eyepiece end face lOOOA of the image guide 1000 according to the distribution of the portions for permitting transmission of light (that is, core portions of the fiber elements) and the portions for inhibiting transmission of light in the image guide 1000.
In general, the net pattern or the pixel arrangement on the output plane of the image guide 1000 does not correspond to the pixel arrangement of image pickup device of the television camera 1400. Therefore, it is well known in the art that a moire pattern will be caused in the enlarged image displayed on the image screen of the monitor 1600 by the interference between the net pattern and the pixel arrangement of the image pickup device. The moire pattern adversely influences the observation of the enlarged image of the internal portion of the blood vessel displayed on the image screen of the monitor 1600.
In order to suppress the intensity of the moire pattern, in the prior art system, an image on the output plane of the image guide 1000 is captured by the television camera 1400 with the point of focus slightly deviated or a low-pass filter is provided in the eye piece 1200.
However, when the intensity of the moire pattern is suppressed, in the above system, the resolution of the image will be lowered with a decrease in the moire pattern and the contour of the endoscopic image to be observed becomes unclear, making it difficult to correctly diagnose the condition of the diseased part.